Can Blood Flow Restriction Augment Submaximal Resistance Exercise-induced Hypoalgesia?

Evidence supports that an acute bout of low load resistance exercise with blood flow restriction (BFR) can induce hypoalgesia, as measured by increased pressure pain thresholds (PPTs). It is not clear whether the increased PPTs can be ascribed solely to the application of BFR or to its ability to reduce the number of repetitions necessary for hypoalgesia. PURPOSE: To determine the effects of BFR on upper and lower body PPTs, specifically using submaximal resistance exercise protocols that accounted for proximity to task failure. METHODS: Forty-four participants (18-35 years) completed five visits. Visit 1 consisted of one-repetition maximum (1RM) testing, after which participants completed two sets of 30% 1RM knee extension exercise to failure (i.e., maximal repetitions) with BFR and without BFR on the dominant and nondominant leg, respectively. The maximal repetitions were used to prescribe repetitions for the exercise conditions. Participants were randomly assigned to perform four experimental conditions on visits 2-5: 1) 70% maximal blood flow restricted repetitions with BFR (LL + BFR); 2) 70% maximal blood flow restricted repetitions without BFR (LL) 3) 70% maximal free flow repetitions (LL + EFFORT); 4) time-matched, non-exercise control (CON). Upper and then lower body PPTs were measured before and after each experimental condition. Bayesian repeated measures ANOVA was used to detect differences between conditions. Data are presented as mean (SD). RESULTS: There was evidence that both upper body PPT (BF10: 86.315) and lower body PPT (BF10: 1.786x106 ) changed differently across conditions. The change in upper body PPT was greater for LL + BFR compared to LL [BF10: 6.341; difference of 0.15 (0.35) kg/cm2], LL + EFFORT [BF10: 23.274; difference of 0.23 (0.45) kg/cm2], and the CON condition (BF10: 130.357; difference of 0.22 (0.35) kg/cm2]. The change in lower body PPT was also greater for LL + BFR compared to LL [BF10: 1499.078; difference of 0.40 (0.55) kg/cm2], LL + EFFORT [BF10: 71.415; difference of 0.36 (0.62) kg/cm2], and the CON condition [BF10: 652243.791; difference of 0.57 (0.56) kg/cm2]. CONCLUSIONS: Submaximal low load resistance exercise with BFR resulted in systemic increases in PPT. The increased PPTs appear to be unique to BFR given that we did not observe changes in the other exercise conditions.